Hoping for a bit of quick help. I'll take it back to the shop tomorrow but I'd like to fix it myself today.

I recently put a Record Groupset on my frame but the shop didn't have a Campag freehub in stock to convert my Fulcrum wheels over. The bike has ridden quite well for two weeks with a Shimano cassette and Campag chain. Yesterday I had the freehub and Campag cassette installed and now when I try to ride the bike on the small front chainring and in the three smallest rear cogs the derailleur jumps. It is not trying to change gears by the looks, it just sort of pings backwards and forwards. Any ideas?

Really you wouldn't ride in those combinations that much...you would usually put it in the big ring for the smallest cogs on the back.But they should still be able to cope either way.Will it back pedal smoothly?...if it jumps off back pedaling it is out of adjust.Did you readjust the limits when you fited the new freewheel?...there might be a bit of difference in the two systems.Did you take the chain off when you did this as well?.

Cambo wrote:I just tested it again and it appears that it is in fact the chain slipping. It is doing it on both chainrings and across from the smallest rear cog to about number five.

MG. It's a brand new Campag Ultra-Narrow chain on a secondhand Campag cassette.

Possibly the cassette is too far worn for the new chain. Replace the cassette for a new one immediately or you risk trashing your chain.

I had this recently when I put a new Wippermann 908 chain on my Cannondale Jekyll offroader that I acquired secondhand. I put a new Shimano LX cassette on it, and after a bit of adjustment for the slightly-changed offset (had SRAM on previously) all has been fine.